1. Field of the Invention
The present invention relates to noise gate control circuitry for electronic systems. More particularly, the present invention relates to noise gate control circuitry for audio systems which eliminates the turn on and turn off effects on speakers.
2. Description of the Related Art
It is often the case when electronic systems are able to render intended disturbances, that there are times when the rendering of unintended disturbances is affected such as when power is applied or removed from the electronic system, or at times when no disturbing effects are desired. For example, a car stereo system produces a disturbance via electronic circuitry that human hearing responds to. However, any disturbance not related to the desired sound program can be vexing to the listener. For example, sounds often occur when the system is turned on and off, and often johnston hiss noises and engine noises can be heard through the speakers when the program signal level drops low enough.
Currently, devices exist which interrupt or attenuate signals when their signal levels drop below given thresholds. In this way, when the program source signal drops to a level low enough that such undesirable noises dominate, the signal is automatically muted or attenuated. However, none of these devices act on the electrical connection between the transducer of a speaker and the source of electrical excitation. Typically these devices respond to the signal level of the source signal after it has been averaged by a low pass filter. Upon responding, some of these devices shift the level at which their state of response changes so as to delay further response until significant enough changes in level for a long enough period of time are sensed. These delays vary with the level of the signal and thus often compromise the desired results.
Devices also exist which connect transducers to a source of electrical excitation only after a delay when a remote power control signal is detected. In this way any turn on transients that might exist in the electrical power source will be avoided until the power source settles to its normal operating state. However, None of these devices coordinate the disconnect of the transducer and the remote turnoff control of the transducer's power source.